Integrated indirectly-converting X-ray detectors can be used in X-ray imaging, for example in computed tomography, angiography or radiography. The X-rays or photons can be converted in indirectly-converting X-ray detectors into light by a suitable converter material and into electric pulses by way of photodiodes. Frequently scintillators, for example GOS (Gd2O2S), CsJ, YGO or LuTAG are used as the converter material. Scintillators are in particular used in medical X-ray imaging in the energy range of up to 1 MeV.
So-called indirectly-converting X-ray detectors, so-called scintillator detectors, are typically used in which the X-rays or gamma rays are converted into electric signals in two stages. In a first stage, the X-ray or gamma quanta are absorbed in a sub-region of the scintillator unit and converted into optical visible light, a light quantity; this effect is called luminescence. The light excited by luminescence is then converted in a second stage by a first photodiode optically coupled to the scintillator unit in a sub-region of an evaluation unit into an electric signal, read out via an electronic evaluation or readout device and then forwarded to a computing unit.
The sub-regions of the scintillator unit and the evaluation unit are as a rule subdivided such that a sub-region of the evaluation unit is assigned to each sub-region of the scintillator unit. This is then referred to as a pixelated X-ray detector. X-ray detectors such as those used in computed tomography, for example, are typically made up of a plurality of modules, which comprise a scattered radiation grid, a scintillator unit, an evaluation unit with photosensors or photodiodes, for example as a photodiode array, and with electronic units for converting the analog signal into digital information and a mechanical carrier. The scattered radiation grid is used to suppress scattered radiation. The mechanical carrier is used to mount the scattered radiation grid, the scintillator unit and the evaluation unit. The scattered radiation grid, scintillator unit and photodiode are typically pixelated in the same way in two directions, for example into rectangular or square pixels. In order to achieve good dose utilization and simultaneously low crosstalk between the pixels, the scattered radiation grid, scintillator unit and photodiode are positioned very exactly with respect to one another when assembling the modules.
When assembling the modules, the scintillator unit or the scintillator array are permanently attached to the photodiode array with the aid of an optical adhesive and aligned at the same time. Both are then secured together on the mechanical carrier or the mechanical module unit. The scattered radiation grid is then also permanently connected to the module, either by bonding with the scintillator array or by way of mechanical fixation on the mechanical carrier, wherein once again optimal positioning with respect to the scintillator array is to be achieved. Finally, the modules pre-assembled in this way are secured in the housing of the detector or the module-receiving appliance. In this case, suitable measures, for example stop surfaces, locating pins or the like ensure that the grip openings of the scattered radiation grid are aligned as well as possible with the tube focus.
Publication DE 102010062192 B3 discloses a 2D collimator for a radiation detector with 2D collimator modules arranged in series, wherein adjacent 2D collimator modules are glued together to establish a fixed mechanical connection to facing module sides and wherein, on their free-remaining side, the outer 2D collimator modules have a retaining element for mounting the 2D collimator opposite a detector mechanism.
Publication DE 102010020610 A1 discloses a radiation detector comprising a scintillator with septa for separating scintillator elements arranged alongside one another and a collimator with webs for forming laterally enclosed radiation channels, wherein the webs are inserted into the septa in order to avoid crosstalk between adjacent scintillator elements.
Publication DE 10335125 B4 discloses a method for producing a luminescent body for an X-ray detector, in particular for X-ray computed tomography scanners, which is made of a ceramic with the general composition (M1-xLnx)2O2S, M being at least one element selected from the group: Y, La, Sc, Lu and/or Gd, and Ln being at least one element selected from the group: Eu, Ce, Pr, Tb, Yb, Dy, Sm and/or Ho.